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An antioxidant might lead to new therapies for bone arthritis

A new treatment for osteoarthritis could soon be in the works

Peter Dazeley/Getty

By Andy Coghlan

An antioxidant food supplement widely used to treat conditions including paracetamol poisoning has shown promise in helping mice with osteoarthritis, the most common joint disorder in the world. The only existing treatments are painkillers and drugs that reduce inflammation, but nothing halts or reverses the condition.

When researchers added N-acetyl cysteine, or NAC, to the drinking water they gave to mice with osteoarthritis, it reduced the level of joint damage to that seen in healthy, control mice. The main effect of the NAC was to stifle damage to cartilage tissue in joints, which is caused by a natural process in cells called oxidative stress.

Rik Lories of the Catholic University of Leuven in Belgium, and his colleagues screened gene activity in cartilage samples from people and mice with osteoarthritis. They discovered depleted levels of a protein called ANP32A. Further gene-profiling experiments in diseased and healthy joint cartilage cells revealed that ANP32A drives production of a natural enzyme which halts oxidative stress.

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This suggests oxidative stress in cartilage cells is a key cause of osteoarthritis – and that a therapy to neutralise the problem could treat the condition. Lories and his team decided to find out using NAC – an antioxidant which neutralises oxidative stress.

When the researchers bred mice unable to make ANP32A, the animals developed severe osteoarthritis. But treating them with NAC healed their joints, reducing cartilage damage to levels seen in healthy control animals.

Lories says that in people with osteoarthritis, NAC may not reach cartilage in sufficient amounts to heal damage. His team plans to focus instead on finding ways to boost ANP32A. “Restoration of its [natural] levels in osteoarthritic cartilage may provide better protection against oxidative stress,” he says.